vires

Vires is the Latin plural form of vis, meaning powers, forces, or energies. In English, the term appears chiefly in formal contexts, particularly in law and in discussions of classical literature or philosophy.

Etymology: from Latin vis, “strength, force,” with vires as the neuter plural. In English usage, vires is usually found as part of set phrases rather than as an independent term.

Legal usage: The most familiar use is ultra vires, meaning beyond the powers conferred by a statute, charter, or constitution. Intra vires means within those powers. The doctrine is employed to determine whether actions by corporations, government bodies, or other authorities are legally authorized. If an act is ultra vires, it may be void or voidable, and remedies or challenges may arise in courts; the precise effects vary by jurisdiction.

Other uses: In classical Latin, vires denotes strength or forces and can describe the power of rulers, gods, or armies. In modern English it survives primarily in the phrases ultra vires and intra vires, and in scholarly or historical writing as a general reference to power or capacity.